irqchip/loongarch: Adjust acpi_cascade_irqdomain_init() and sub-routines

1, Adjust the return of acpi_cascade_irqdomain_init() and check its
   return value.
2, Combine unnecessary short lines to one long line.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221020142514.1725514-1-chenhuacai@loongson.cn